You're assuming that the confusion isn't intentional. It is, to make people sign up for Google+ while disguising it as a identity service.

And more and more normal customers seem to be noticing, especially on Youtube. Here's one woman crying about about how the confusing G+ prompts lead her to lose all her uploaded videos. (Warning, strong language) https://www.youtube.com/watch?v=Ccxiwu4MaJs